linux/Documentation/kernel-parameters.txt
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   1                          Kernel Parameters
   2                          ~~~~~~~~~~~~~~~~~
   3
   4The following is a consolidated list of the kernel parameters as implemented
   5(mostly) by the __setup() macro and sorted into English Dictionary order
   6(defined as ignoring all punctuation and sorting digits before letters in a
   7case insensitive manner), and with descriptions where known.
   8
   9Module parameters for loadable modules are specified only as the
  10parameter name with optional '=' and value as appropriate, such as:
  11
  12        modprobe usbcore blinkenlights=1
  13
  14Module parameters for modules that are built into the kernel image
  15are specified on the kernel command line with the module name plus
  16'.' plus parameter name, with '=' and value if appropriate, such as:
  17
  18        usbcore.blinkenlights=1
  19
  20Hyphens (dashes) and underscores are equivalent in parameter names, so
  21        log_buf_len=1M print-fatal-signals=1
  22can also be entered as
  23        log-buf-len=1M print_fatal_signals=1
  24
  25
  26This document may not be entirely up to date and comprehensive. The command
  27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  28module. Loadable modules, after being loaded into the running kernel, also
  29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  30parameters may be changed at runtime by the command
  31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  32
  33The parameters listed below are only valid if certain kernel build options were
  34enabled and if respective hardware is present. The text in square brackets at
  35the beginning of each description states the restrictions within which a
  36parameter is applicable:
  37
  38        ACPI    ACPI support is enabled.
  39        AGP     AGP (Accelerated Graphics Port) is enabled.
  40        ALSA    ALSA sound support is enabled.
  41        APIC    APIC support is enabled.
  42        APM     Advanced Power Management support is enabled.
  43        AVR32   AVR32 architecture is enabled.
  44        AX25    Appropriate AX.25 support is enabled.
  45        BLACKFIN Blackfin architecture is enabled.
  46        DRM     Direct Rendering Management support is enabled.
  47        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  48        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  49        EFI     EFI Partitioning (GPT) is enabled
  50        EIDE    EIDE/ATAPI support is enabled.
  51        FB      The frame buffer device is enabled.
  52        GCOV    GCOV profiling is enabled.
  53        HW      Appropriate hardware is enabled.
  54        IA-64   IA-64 architecture is enabled.
  55        IMA     Integrity measurement architecture is enabled.
  56        IOSCHED More than one I/O scheduler is enabled.
  57        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  58        IPV6    IPv6 support is enabled.
  59        ISAPNP  ISA PnP code is enabled.
  60        ISDN    Appropriate ISDN support is enabled.
  61        JOY     Appropriate joystick support is enabled.
  62        KGDB    Kernel debugger support is enabled.
  63        KVM     Kernel Virtual Machine support is enabled.
  64        LIBATA  Libata driver is enabled
  65        LP      Printer support is enabled.
  66        LOOP    Loopback device support is enabled.
  67        M68k    M68k architecture is enabled.
  68                        These options have more detailed description inside of
  69                        Documentation/m68k/kernel-options.txt.
  70        MCA     MCA bus support is enabled.
  71        MDA     MDA console support is enabled.
  72        MOUSE   Appropriate mouse support is enabled.
  73        MSI     Message Signaled Interrupts (PCI).
  74        MTD     MTD (Memory Technology Device) support is enabled.
  75        NET     Appropriate network support is enabled.
  76        NUMA    NUMA support is enabled.
  77        NFS     Appropriate NFS support is enabled.
  78        OSS     OSS sound support is enabled.
  79        PV_OPS  A paravirtualized kernel is enabled.
  80        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  81        PARISC  The PA-RISC architecture is enabled.
  82        PCI     PCI bus support is enabled.
  83        PCIE    PCI Express support is enabled.
  84        PCMCIA  The PCMCIA subsystem is enabled.
  85        PNP     Plug & Play support is enabled.
  86        PPC     PowerPC architecture is enabled.
  87        PPT     Parallel port support is enabled.
  88        PS2     Appropriate PS/2 support is enabled.
  89        RAM     RAM disk support is enabled.
  90        S390    S390 architecture is enabled.
  91        SCSI    Appropriate SCSI support is enabled.
  92                        A lot of drivers have their options described inside
  93                        the Documentation/scsi/ sub-directory.
  94        SECURITY Different security models are enabled.
  95        SELINUX SELinux support is enabled.
  96        APPARMOR AppArmor support is enabled.
  97        SERIAL  Serial support is enabled.
  98        SH      SuperH architecture is enabled.
  99        SMP     The kernel is an SMP kernel.
 100        SPARC   Sparc architecture is enabled.
 101        SWSUSP  Software suspend (hibernation) is enabled.
 102        SUSPEND System suspend states are enabled.
 103        FTRACE  Function tracing enabled.
 104        TPM     TPM drivers are enabled.
 105        TS      Appropriate touchscreen support is enabled.
 106        UMS     USB Mass Storage support is enabled.
 107        USB     USB support is enabled.
 108        USBHID  USB Human Interface Device support is enabled.
 109        V4L     Video For Linux support is enabled.
 110        VGA     The VGA console has been enabled.
 111        VT      Virtual terminal support is enabled.
 112        WDT     Watchdog support is enabled.
 113        XT      IBM PC/XT MFM hard disk support is enabled.
 114        X86-32  X86-32, aka i386 architecture is enabled.
 115        X86-64  X86-64 architecture is enabled.
 116                        More X86-64 boot options can be found in
 117                        Documentation/x86/x86_64/boot-options.txt .
 118        X86     Either 32bit or 64bit x86 (same as X86-32+X86-64)
 119        XEN     Xen support is enabled
 120
 121In addition, the following text indicates that the option:
 122
 123        BUGS=   Relates to possible processor bugs on the said processor.
 124        KNL     Is a kernel start-up parameter.
 125        BOOT    Is a boot loader parameter.
 126
 127Parameters denoted with BOOT are actually interpreted by the boot
 128loader, and have no meaning to the kernel directly.
 129Do not modify the syntax of boot loader parameters without extreme
 130need or coordination with <Documentation/x86/boot.txt>.
 131
 132There are also arch-specific kernel-parameters not documented here.
 133See for example <Documentation/x86/x86_64/boot-options.txt>.
 134
 135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 136a trailing = on the name of any parameter states that that parameter will
 137be entered as an environment variable, whereas its absence indicates that
 138it will appear as a kernel argument readable via /proc/cmdline by programs
 139running once the system is up.
 140
 141The number of kernel parameters is not limited, but the length of the
 142complete command line (parameters including spaces etc.) is limited to
 143a fixed number of characters. This limit depends on the architecture
 144and is between 256 and 4096 characters. It is defined in the file
 145./include/asm/setup.h as COMMAND_LINE_SIZE.
 146
 147Finally, the [KMG] suffix is commonly described after a number of kernel
 148parameter values. These 'K', 'M', and 'G' letters represent the _binary_
 149multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
 150bytes respectively. Such letter suffixes can also be entirely omitted.
 151
 152
 153        acpi=           [HW,ACPI,X86]
 154                        Advanced Configuration and Power Interface
 155                        Format: { force | off | strict | noirq | rsdt }
 156                        force -- enable ACPI if default was off
 157                        off -- disable ACPI if default was on
 158                        noirq -- do not use ACPI for IRQ routing
 159                        strict -- Be less tolerant of platforms that are not
 160                                strictly ACPI specification compliant.
 161                        rsdt -- prefer RSDT over (default) XSDT
 162                        copy_dsdt -- copy DSDT to memory
 163
 164                        See also Documentation/power/pm.txt, pci=noacpi
 165
 166        acpi_apic_instance=     [ACPI, IOAPIC]
 167                        Format: <int>
 168                        2: use 2nd APIC table, if available
 169                        1,0: use 1st APIC table
 170                        default: 0
 171
 172        acpi_backlight= [HW,ACPI]
 173                        acpi_backlight=vendor
 174                        acpi_backlight=video
 175                        If set to vendor, prefer vendor specific driver
 176                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 177                        of the ACPI video.ko driver.
 178
 179        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 180        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 181                        Format: <int>
 182                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 183                        debug output.  Bits in debug_layer correspond to a
 184                        _COMPONENT in an ACPI source file, e.g.,
 185                            #define _COMPONENT ACPI_PCI_COMPONENT
 186                        Bits in debug_level correspond to a level in
 187                        ACPI_DEBUG_PRINT statements, e.g.,
 188                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 189                        The debug_level mask defaults to "info".  See
 190                        Documentation/acpi/debug.txt for more information about
 191                        debug layers and levels.
 192
 193                        Enable processor driver info messages:
 194                            acpi.debug_layer=0x20000000
 195                        Enable PCI/PCI interrupt routing info messages:
 196                            acpi.debug_layer=0x400000
 197                        Enable AML "Debug" output, i.e., stores to the Debug
 198                        object while interpreting AML:
 199                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 200                        Enable all messages related to ACPI hardware:
 201                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 202
 203                        Some values produce so much output that the system is
 204                        unusable.  The "log_buf_len" parameter may be useful
 205                        if you need to capture more output.
 206
 207        acpi_irq_balance [HW,ACPI]
 208                        ACPI will balance active IRQs
 209                        default in APIC mode
 210
 211        acpi_irq_nobalance [HW,ACPI]
 212                        ACPI will not move active IRQs (default)
 213                        default in PIC mode
 214
 215        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 216                        Format: <irq>,<irq>...
 217
 218        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 219                        use by PCI
 220                        Format: <irq>,<irq>...
 221
 222        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 223
 224        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 225                        Format: To spoof as Windows 98: ="Microsoft Windows"
 226
 227        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 228                        acpi_osi="string1"      # add string1 -- only one string
 229                        acpi_osi="!string2"     # remove built-in string2
 230                        acpi_osi=               # disable all strings
 231
 232        acpi_pm_good    [X86]
 233                        Override the pmtimer bug detection: force the kernel
 234                        to assume that this machine's pmtimer latches its value
 235                        and always returns good values.
 236
 237        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 238                        Format: { level | edge | high | low }
 239
 240        acpi_serialize  [HW,ACPI] force serialization of AML methods
 241
 242        acpi_skip_timer_override [HW,ACPI]
 243                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 244                        For broken nForce2 BIOS resulting in XT-PIC timer.
 245
 246        acpi_sleep=     [HW,ACPI] Sleep options
 247                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 248                                  old_ordering, s4_nonvs, sci_force_enable }
 249                        See Documentation/power/video.txt for information on
 250                        s3_bios and s3_mode.
 251                        s3_beep is for debugging; it makes the PC's speaker beep
 252                        as soon as the kernel's real-mode entry point is called.
 253                        s4_nohwsig prevents ACPI hardware signature from being
 254                        used during resume from hibernation.
 255                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 256                        control method, with respect to putting devices into
 257                        low power states, to be enforced (the ACPI 2.0 ordering
 258                        of _PTS is used by default).
 259                        nonvs prevents the kernel from saving/restoring the
 260                        ACPI NVS memory during suspend/hibernation and resume.
 261                        sci_force_enable causes the kernel to set SCI_EN directly
 262                        on resume from S1/S3 (which is against the ACPI spec,
 263                        but some broken systems don't work without it).
 264
 265        acpi_use_timer_override [HW,ACPI]
 266                        Use timer override. For some broken Nvidia NF5 boards
 267                        that require a timer override, but don't have HPET
 268
 269        acpi_enforce_resources= [ACPI]
 270                        { strict | lax | no }
 271                        Check for resource conflicts between native drivers
 272                        and ACPI OperationRegions (SystemIO and SystemMemory
 273                        only). IO ports and memory declared in ACPI might be
 274                        used by the ACPI subsystem in arbitrary AML code and
 275                        can interfere with legacy drivers.
 276                        strict (default): access to resources claimed by ACPI
 277                        is denied; legacy drivers trying to access reserved
 278                        resources will fail to bind to device using them.
 279                        lax: access to resources claimed by ACPI is allowed;
 280                        legacy drivers trying to access reserved resources
 281                        will bind successfully but a warning message is logged.
 282                        no: ACPI OperationRegions are not marked as reserved,
 283                        no further checks are performed.
 284
 285        add_efi_memmap  [EFI; X86] Include EFI memory map in
 286                        kernel's map of available physical RAM.
 287
 288        agp=            [AGP]
 289                        { off | try_unsupported }
 290                        off: disable AGP support
 291                        try_unsupported: try to drive unsupported chipsets
 292                                (may crash computer or cause data corruption)
 293
 294        ALSA            [HW,ALSA]
 295                        See Documentation/sound/alsa/alsa-parameters.txt
 296
 297        alignment=      [KNL,ARM]
 298                        Allow the default userspace alignment fault handler
 299                        behaviour to be specified.  Bit 0 enables warnings,
 300                        bit 1 enables fixups, and bit 2 sends a segfault.
 301
 302        amd_iommu=      [HW,X86-84]
 303                        Pass parameters to the AMD IOMMU driver in the system.
 304                        Possible values are:
 305                        fullflush - enable flushing of IO/TLB entries when
 306                                    they are unmapped. Otherwise they are
 307                                    flushed before they will be reused, which
 308                                    is a lot of faster
 309                        off       - do not initialize any AMD IOMMU found in
 310                                    the system
 311
 312        amijoy.map=     [HW,JOY] Amiga joystick support
 313                        Map of devices attached to JOY0DAT and JOY1DAT
 314                        Format: <a>,<b>
 315                        See also Documentation/kernel/input/joystick.txt
 316
 317        analog.map=     [HW,JOY] Analog joystick and gamepad support
 318                        Specifies type or capabilities of an analog joystick
 319                        connected to one of 16 gameports
 320                        Format: <type1>,<type2>,..<type16>
 321
 322        apc=            [HW,SPARC]
 323                        Power management functions (SPARCstation-4/5 + deriv.)
 324                        Format: noidle
 325                        Disable APC CPU standby support. SPARCstation-Fox does
 326                        not play well with APC CPU idle - disable it if you have
 327                        APC and your system crashes randomly.
 328
 329        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 330                        Change the output verbosity whilst booting
 331                        Format: { quiet (default) | verbose | debug }
 332                        Change the amount of debugging information output
 333                        when initialising the APIC and IO-APIC components.
 334
 335        autoconf=       [IPV6]
 336                        See Documentation/networking/ipv6.txt.
 337
 338        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
 339                        Limit apic dumping. The parameter defines the maximal
 340                        number of local apics being dumped. Also it is possible
 341                        to set it to "all" by meaning -- no limit here.
 342                        Format: { 1 (default) | 2 | ... | all }.
 343                        The parameter valid if only apic=debug or
 344                        apic=verbose is specified.
 345                        Example: apic=debug show_lapic=all
 346
 347        apm=            [APM] Advanced Power Management
 348                        See header of arch/x86/kernel/apm_32.c.
 349
 350        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 351                        Format: <io>,<irq>,<nodeID>
 352
 353        ataflop=        [HW,M68k]
 354
 355        atarimouse=     [HW,MOUSE] Atari Mouse
 356
 357        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 358                        EzKey and similar keyboards
 359
 360        atkbd.reset=    [HW] Reset keyboard during initialization
 361
 362        atkbd.set=      [HW] Select keyboard code set
 363                        Format: <int> (2 = AT (default), 3 = PS/2)
 364
 365        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 366                        keyboards
 367
 368        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 369                        Format: <bool> (0 = real, 1 = synthetic (default))
 370
 371        atkbd.softrepeat= [HW]
 372                        Use software keyboard repeat
 373
 374        autotest        [IA64]
 375
 376        baycom_epp=     [HW,AX25]
 377                        Format: <io>,<mode>
 378
 379        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 380                        Format: <io>,<mode>
 381                        See header of drivers/net/hamradio/baycom_par.c.
 382
 383        baycom_ser_fdx= [HW,AX25]
 384                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 385                        Format: <io>,<irq>,<mode>[,<baud>]
 386                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 387
 388        baycom_ser_hdx= [HW,AX25]
 389                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 390                        Format: <io>,<irq>,<mode>
 391                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 392
 393        boot_delay=     Milliseconds to delay each printk during boot.
 394                        Values larger than 10 seconds (10000) are changed to
 395                        no delay (0).
 396                        Format: integer
 397
 398        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 399
 400        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 401        bttv.radio=     Most important insmod options are available as
 402                        kernel args too.
 403        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 404        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 405
 406        bulk_remove=off [PPC]  This parameter disables the use of the pSeries
 407                        firmware feature for flushing multiple hpte entries
 408                        at a time.
 409
 410        c101=           [NET] Moxa C101 synchronous serial card
 411
 412        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 413                        Sometimes CPU hardware bugs make them report the cache
 414                        size incorrectly. The kernel will attempt work arounds
 415                        to fix known problems, but for some CPUs it is not
 416                        possible to determine what the correct size should be.
 417                        This option provides an override for these situations.
 418
 419        capability.disable=
 420                        [SECURITY] Disable capabilities.  This would normally
 421                        be used only if an alternative security model is to be
 422                        configured.  Potentially dangerous and should only be
 423                        used if you are entirely sure of the consequences.
 424
 425        ccw_timeout_log [S390]
 426                        See Documentation/s390/CommonIO for details.
 427
 428        cgroup_disable= [KNL] Disable a particular controller
 429                        Format: {name of the controller(s) to disable}
 430                                {Currently supported controllers - "memory"}
 431
 432        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 433                        Format: { "0" | "1" }
 434                        See security/selinux/Kconfig help text.
 435                        0 -- check protection applied by kernel (includes
 436                                any implied execute protection).
 437                        1 -- check protection requested by application.
 438                        Default value is set via a kernel config option.
 439                        Value can be changed at runtime via
 440                                /selinux/checkreqprot.
 441
 442        cio_ignore=     [S390]
 443                        See Documentation/s390/CommonIO for details.
 444
 445        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 446                        [Deprecated]
 447                        Forces specified clocksource (if available) to be used
 448                        when calculating gettimeofday(). If specified
 449                        clocksource is not available, it defaults to PIT.
 450                        Format: { pit | tsc | cyclone | pmtmr }
 451
 452        clocksource=    Override the default clocksource
 453                        Format: <string>
 454                        Override the default clocksource and use the clocksource
 455                        with the name specified.
 456                        Some clocksource names to choose from, depending on
 457                        the platform:
 458                        [all] jiffies (this is the base, fallback clocksource)
 459                        [ACPI] acpi_pm
 460                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 461                                pxa_timer,timer3,32k_counter,timer0_1
 462                        [AVR32] avr32
 463                        [X86-32] pit,hpet,tsc;
 464                                scx200_hrt on Geode; cyclone on IBM x440
 465                        [MIPS] MIPS
 466                        [PARISC] cr16
 467                        [S390] tod
 468                        [SH] SuperH
 469                        [SPARC64] tick
 470                        [X86-64] hpet,tsc
 471
 472        clearcpuid=BITNUM [X86]
 473                        Disable CPUID feature X for the kernel. See
 474                        arch/x86/include/asm/cpufeature.h for the valid bit
 475                        numbers. Note the Linux specific bits are not necessarily
 476                        stable over kernel options, but the vendor specific
 477                        ones should be.
 478                        Also note that user programs calling CPUID directly
 479                        or using the feature without checking anything
 480                        will still see it. This just prevents it from
 481                        being used by the kernel or shown in /proc/cpuinfo.
 482                        Also note the kernel might malfunction if you disable
 483                        some critical bits.
 484
 485        cmo_free_hint=  [PPC] Format: { yes | no }
 486                        Specify whether pages are marked as being inactive
 487                        when they are freed.  This is used in CMO environments
 488                        to determine OS memory pressure for page stealing by
 489                        a hypervisor.
 490                        Default: yes
 491
 492        code_bytes      [X86] How many bytes of object code to print
 493                        in an oops report.
 494                        Range: 0 - 8192
 495                        Default: 64
 496
 497        com20020=       [HW,NET] ARCnet - COM20020 chipset
 498                        Format:
 499                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 500
 501        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 502                        Format: <io>[,<irq>]
 503
 504        com90xx=        [HW,NET]
 505                        ARCnet - COM90xx chipset (memory-mapped buffers)
 506                        Format: <io>[,<irq>[,<memstart>]]
 507
 508        condev=         [HW,S390] console device
 509        conmode=
 510
 511        console=        [KNL] Output console device and options.
 512
 513                tty<n>  Use the virtual console device <n>.
 514
 515                ttyS<n>[,options]
 516                ttyUSB0[,options]
 517                        Use the specified serial port.  The options are of
 518                        the form "bbbbpnf", where "bbbb" is the baud rate,
 519                        "p" is parity ("n", "o", or "e"), "n" is number of
 520                        bits, and "f" is flow control ("r" for RTS or
 521                        omit it).  Default is "9600n8".
 522
 523                        See Documentation/serial-console.txt for more
 524                        information.  See
 525                        Documentation/networking/netconsole.txt for an
 526                        alternative.
 527
 528                uart[8250],io,<addr>[,options]
 529                uart[8250],mmio,<addr>[,options]
 530                        Start an early, polled-mode console on the 8250/16550
 531                        UART at the specified I/O port or MMIO address,
 532                        switching to the matching ttyS device later.  The
 533                        options are the same as for ttyS, above.
 534
 535                If the device connected to the port is not a TTY but a braille
 536                device, prepend "brl," before the device type, for instance
 537                        console=brl,ttyS0
 538                For now, only VisioBraille is supported.
 539
 540        consoleblank=   [KNL] The console blank (screen saver) timeout in
 541                        seconds. Defaults to 10*60 = 10mins. A value of 0
 542                        disables the blank timer.
 543
 544        coredump_filter=
 545                        [KNL] Change the default value for
 546                        /proc/<pid>/coredump_filter.
 547                        See also Documentation/filesystems/proc.txt.
 548
 549        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 550                        Format:
 551                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 552
 553        crashkernel=size[KMG][@offset[KMG]]
 554                        [KNL] Using kexec, Linux can switch to a 'crash kernel'
 555                        upon panic. This parameter reserves the physical
 556                        memory region [offset, offset + size] for that kernel
 557                        image. If '@offset' is omitted, then a suitable offset
 558                        is selected automatically. Check
 559                        Documentation/kdump/kdump.txt for further details.
 560
 561        crashkernel=range1:size1[,range2:size2,...][@offset]
 562                        [KNL] Same as above, but depends on the memory
 563                        in the running system. The syntax of range is
 564                        start-[end] where start and end are both
 565                        a memory unit (amount[KMG]). See also
 566                        Documentation/kdump/kdump.txt for an example.
 567
 568        cs89x0_dma=     [HW,NET]
 569                        Format: <dma>
 570
 571        cs89x0_media=   [HW,NET]
 572                        Format: { rj45 | aui | bnc }
 573
 574        dasd=           [HW,NET]
 575                        See header of drivers/s390/block/dasd_devmap.c.
 576
 577        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 578                        (one device per port)
 579                        Format: <port#>,<type>
 580                        See also Documentation/input/joystick-parport.txt
 581
 582        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
 583                        time. See Documentation/dynamic-debug-howto.txt for
 584                        details.
 585
 586        debug           [KNL] Enable kernel debugging (events log level).
 587
 588        debug_locks_verbose=
 589                        [KNL] verbose self-tests
 590                        Format=<0|1>
 591                        Print debugging info while doing the locking API
 592                        self-tests.
 593                        We default to 0 (no extra messages), setting it to
 594                        1 will print _a lot_ more information - normally
 595                        only useful to kernel developers.
 596
 597        debug_objects   [KNL] Enable object debugging
 598
 599        no_debug_objects
 600                        [KNL] Disable object debugging
 601
 602        debugpat        [X86] Enable PAT debugging
 603
 604        decnet.addr=    [HW,NET]
 605                        Format: <area>[,<node>]
 606                        See also Documentation/networking/decnet.txt.
 607
 608        default_hugepagesz=
 609                        [same as hugepagesz=] The size of the default
 610                        HugeTLB page size. This is the size represented by
 611                        the legacy /proc/ hugepages APIs, used for SHM, and
 612                        default size when mounting hugetlbfs filesystems.
 613                        Defaults to the default architecture's huge page size
 614                        if not specified.
 615
 616        dhash_entries=  [KNL]
 617                        Set number of hash buckets for dentry cache.
 618
 619        digi=           [HW,SERIAL]
 620                        IO parameters + enable/disable command.
 621
 622        digiepca=       [HW,SERIAL]
 623                        See drivers/char/README.epca and
 624                        Documentation/serial/digiepca.txt.
 625
 626        disable=        [IPV6]
 627                        See Documentation/networking/ipv6.txt.
 628
 629        disable_ipv6=   [IPV6]
 630                        See Documentation/networking/ipv6.txt.
 631
 632        disable_mtrr_cleanup [X86]
 633                        The kernel tries to adjust MTRR layout from continuous
 634                        to discrete, to make X server driver able to add WB
 635                        entry later. This parameter disables that.
 636
 637        disable_mtrr_trim [X86, Intel and AMD only]
 638                        By default the kernel will trim any uncacheable
 639                        memory out of your available memory pool based on
 640                        MTRR settings.  This parameter disables that behavior,
 641                        possibly causing your machine to run very slowly.
 642
 643        disable_timer_pin_1 [X86]
 644                        Disable PIN 1 of APIC timer
 645                        Can be useful to work around chipset bugs.
 646
 647        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 648                        this option disables the debugging code at boot.
 649
 650        dma_debug_entries=<number>
 651                        This option allows to tune the number of preallocated
 652                        entries for DMA-API debugging code. One entry is
 653                        required per DMA-API allocation. Use this if the
 654                        DMA-API debugging code disables itself because the
 655                        architectural default is too low.
 656
 657        dma_debug_driver=<driver_name>
 658                        With this option the DMA-API debugging driver
 659                        filter feature can be enabled at boot time. Just
 660                        pass the driver to filter for as the parameter.
 661                        The filter can be disabled or changed to another
 662                        driver later using sysfs.
 663
 664        dscc4.setup=    [NET]
 665
 666        earlycon=       [KNL] Output early console device and options.
 667                uart[8250],io,<addr>[,options]
 668                uart[8250],mmio,<addr>[,options]
 669                uart[8250],mmio32,<addr>[,options]
 670                        Start an early, polled-mode console on the 8250/16550
 671                        UART at the specified I/O port or MMIO address.
 672                        MMIO inter-register address stride is either 8bit (mmio)
 673                        or 32bit (mmio32).
 674                        The options are the same as for ttyS, above.
 675
 676        earlyprintk=    [X86,SH,BLACKFIN]
 677                        earlyprintk=vga
 678                        earlyprintk=serial[,ttySn[,baudrate]]
 679                        earlyprintk=ttySn[,baudrate]
 680                        earlyprintk=dbgp[debugController#]
 681
 682                        Append ",keep" to not disable it when the real console
 683                        takes over.
 684
 685                        Only vga or serial or usb debug port at a time.
 686
 687                        Currently only ttyS0 and ttyS1 are supported.
 688
 689                        Interaction with the standard serial driver is not
 690                        very good.
 691
 692                        The VGA output is eventually overwritten by the real
 693                        console.
 694
 695        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
 696                        ekgdboc=kbd
 697
 698                        This is desgined to be used in conjunction with
 699                        the boot argument: earlyprintk=vga
 700
 701        edd=            [EDD]
 702                        Format: {"off" | "on" | "skip[mbr]"}
 703
 704        eisa_irq_edge=  [PARISC,HW]
 705                        See header of drivers/parisc/eisa.c.
 706
 707        elanfreq=       [X86-32]
 708                        See comment before function elanfreq_setup() in
 709                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 710
 711        elevator=       [IOSCHED]
 712                        Format: {"cfq" | "deadline" | "noop"}
 713                        See Documentation/block/as-iosched.txt and
 714                        Documentation/block/deadline-iosched.txt for details.
 715
 716        elfcorehdr=     [IA64,PPC,SH,X86]
 717                        Specifies physical address of start of kernel core
 718                        image elf header. Generally kexec loader will
 719                        pass this option to capture kernel.
 720                        See Documentation/kdump/kdump.txt for details.
 721
 722        enable_mtrr_cleanup [X86]
 723                        The kernel tries to adjust MTRR layout from continuous
 724                        to discrete, to make X server driver able to add WB
 725                        entry later. This parameter enables that.
 726
 727        enable_timer_pin_1 [X86]
 728                        Enable PIN 1 of APIC timer
 729                        Can be useful to work around chipset bugs
 730                        (in particular on some ATI chipsets).
 731                        The kernel tries to set a reasonable default.
 732
 733        enforcing       [SELINUX] Set initial enforcing status.
 734                        Format: {"0" | "1"}
 735                        See security/selinux/Kconfig help text.
 736                        0 -- permissive (log only, no denials).
 737                        1 -- enforcing (deny and log).
 738                        Default value is 0.
 739                        Value can be changed at runtime via /selinux/enforce.
 740
 741        erst_disable    [ACPI]
 742                        Disable Error Record Serialization Table (ERST)
 743                        support.
 744
 745        ether=          [HW,NET] Ethernet cards parameters
 746                        This option is obsoleted by the "netdev=" option, which
 747                        has equivalent usage. See its documentation for details.
 748
 749        failslab=
 750        fail_page_alloc=
 751        fail_make_request=[KNL]
 752                        General fault injection mechanism.
 753                        Format: <interval>,<probability>,<space>,<times>
 754                        See also /Documentation/fault-injection/.
 755
 756        floppy=         [HW]
 757                        See Documentation/blockdev/floppy.txt.
 758
 759        force_pal_cache_flush
 760                        [IA-64] Avoid check_sal_cache_flush which may hang on
 761                        buggy SAL_CACHE_FLUSH implementations. Using this
 762                        parameter will force ia64_sal_cache_flush to call
 763                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 764
 765        ftrace=[tracer]
 766                        [FTRACE] will set and start the specified tracer
 767                        as early as possible in order to facilitate early
 768                        boot debugging.
 769
 770        ftrace_dump_on_oops[=orig_cpu]
 771                        [FTRACE] will dump the trace buffers on oops.
 772                        If no parameter is passed, ftrace will dump
 773                        buffers of all CPUs, but if you pass orig_cpu, it will
 774                        dump only the buffer of the CPU that triggered the
 775                        oops.
 776
 777        ftrace_filter=[function-list]
 778                        [FTRACE] Limit the functions traced by the function
 779                        tracer at boot up. function-list is a comma separated
 780                        list of functions. This list can be changed at run
 781                        time by the set_ftrace_filter file in the debugfs
 782                        tracing directory. 
 783
 784        ftrace_notrace=[function-list]
 785                        [FTRACE] Do not trace the functions specified in
 786                        function-list. This list can be changed at run time
 787                        by the set_ftrace_notrace file in the debugfs
 788                        tracing directory.
 789
 790        ftrace_graph_filter=[function-list]
 791                        [FTRACE] Limit the top level callers functions traced
 792                        by the function graph tracer at boot up.
 793                        function-list is a comma separated list of functions
 794                        that can be changed at run time by the
 795                        set_graph_function file in the debugfs tracing directory.
 796
 797        gamecon.map[2|3]=
 798                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 799                        support via parallel port (up to 5 devices per port)
 800                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 801                        See also Documentation/input/joystick-parport.txt
 802
 803        gamma=          [HW,DRM]
 804
 805        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 806                        Format: off | on
 807                        default: on
 808
 809        gcov_persist=   [GCOV] When non-zero (default), profiling data for
 810                        kernel modules is saved and remains accessible via
 811                        debugfs, even when the module is unloaded/reloaded.
 812                        When zero, profiling data is discarded and associated
 813                        debugfs files are removed at module unload time.
 814
 815        gpt             [EFI] Forces disk with valid GPT signature but
 816                        invalid Protective MBR to be treated as GPT.
 817
 818        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 819                        are distributed across NUMA nodes.  Defaults on
 820                        for 64bit NUMA, off otherwise.
 821                        Format: 0 | 1 (for off | on)
 822
 823        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 824
 825        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 826                        Format: <cyl>,<head>,<sect>
 827
 828        hest_disable    [ACPI]
 829                        Disable Hardware Error Source Table (HEST) support;
 830                        corresponding firmware-first mode error processing
 831                        logic will be disabled.
 832
 833        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 834                        size of <nn>. This works even on boxes that have no
 835                        highmem otherwise. This also works to reduce highmem
 836                        size on bigger boxes.
 837
 838        highres=        [KNL] Enable/disable high resolution timer mode.
 839                        Valid parameters: "on", "off"
 840                        Default: "on"
 841
 842        hisax=          [HW,ISDN]
 843                        See Documentation/isdn/README.HiSax.
 844
 845        hlt             [BUGS=ARM,SH]
 846
 847        hpet=           [X86-32,HPET] option to control HPET usage
 848                        Format: { enable (default) | disable | force |
 849                                verbose }
 850                        disable: disable HPET and use PIT instead
 851                        force: allow force enabled of undocumented chips (ICH4,
 852                                VIA, nVidia)
 853                        verbose: show contents of HPET registers during setup
 854
 855        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 856        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 857                        On x86-64 and powerpc, this option can be specified
 858                        multiple times interleaved with hugepages= to reserve
 859                        huge pages of different sizes. Valid pages sizes on
 860                        x86-64 are 2M (when the CPU supports "pse") and 1G
 861                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 862                        Note that 1GB pages can only be allocated at boot time
 863                        using hugepages= and not freed afterwards.
 864
 865        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 866                               terminal devices. Valid values: 0..8
 867        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
 868                               If specified, z/VM IUCV HVC accepts connections
 869                               from listed z/VM user IDs only.
 870
 871        i2c_bus=        [HW] Override the default board specific I2C bus speed
 872                             or register an additional I2C bus that is not
 873                             registered from board initialization code.
 874                             Format:
 875                             <bus_id>,<clkrate>
 876
 877        i8042.debug     [HW] Toggle i8042 debug mode
 878        i8042.direct    [HW] Put keyboard port into non-translated mode
 879        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 880                             keyboard and cannot control its state
 881                             (Don't attempt to blink the leds)
 882        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 883        i8042.nokbd     [HW] Don't check/create keyboard port
 884        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 885                             for the AUX port
 886        i8042.nomux     [HW] Don't check presence of an active multiplexing
 887                             controller
 888        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 889                             controllers
 890        i8042.notimeout [HW] Ignore timeout condition signalled by conroller
 891        i8042.reset     [HW] Reset the controller during init and cleanup
 892        i8042.unlock    [HW] Unlock (ignore) the keylock
 893
 894        i810=           [HW,DRM]
 895
 896        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 897                        indicates that the driver is running on unsupported
 898                        hardware.
 899        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 900                        does not match list of supported models.
 901        i8k.power_status
 902                        [HW] Report power status in /proc/i8k
 903                        (disabled by default)
 904        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 905                        capability is set.
 906
 907        icn=            [HW,ISDN]
 908                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 909
 910        ide-core.nodma= [HW] (E)IDE subsystem
 911                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
 912                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
 913                        .cdrom .chs .ignore_cable are additional options
 914                        See Documentation/ide/ide.txt.
 915
 916        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
 917                        Claim all unknown PCI IDE storage controllers.
 918
 919        idle=           [X86]
 920                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
 921                        Poll forces a polling idle loop that can slightly
 922                        improve the performance of waking up a idle CPU, but
 923                        will use a lot of power and make the system run hot.
 924                        Not recommended.
 925                        idle=mwait: On systems which support MONITOR/MWAIT but
 926                        the kernel chose to not use it because it doesn't save
 927                        as much power as a normal idle loop, use the
 928                        MONITOR/MWAIT idle loop anyways. Performance should be
 929                        the same as idle=poll.
 930                        idle=halt: Halt is forced to be used for CPU idle.
 931                        In such case C2/C3 won't be used again.
 932                        idle=nomwait: Disable mwait for CPU C-states
 933
 934        ignore_loglevel [KNL]
 935                        Ignore loglevel setting - this will print /all/
 936                        kernel messages to the console. Useful for debugging.
 937
 938        ihash_entries=  [KNL]
 939                        Set number of hash buckets for inode cache.
 940
 941        ima_audit=      [IMA]
 942                        Format: { "0" | "1" }
 943                        0 -- integrity auditing messages. (Default)
 944                        1 -- enable informational integrity auditing messages.
 945
 946        ima_hash=       [IMA]
 947                        Format: { "sha1" | "md5" }
 948                        default: "sha1"
 949
 950        ima_tcb         [IMA]
 951                        Load a policy which meets the needs of the Trusted
 952                        Computing Base.  This means IMA will measure all
 953                        programs exec'd, files mmap'd for exec, and all files
 954                        opened for read by uid=0.
 955
 956        init=           [KNL]
 957                        Format: <full_path>
 958                        Run specified binary instead of /sbin/init as init
 959                        process.
 960
 961        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 962                        for working out where the kernel is dying during
 963                        startup.
 964
 965        initrd=         [BOOT] Specify the location of the initial ramdisk
 966
 967        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 968                        Format: <irq>
 969
 970        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
 971                on
 972                        Enable intel iommu driver.
 973                off
 974                        Disable intel iommu driver.
 975                igfx_off [Default Off]
 976                        By default, gfx is mapped as normal device. If a gfx
 977                        device has a dedicated DMAR unit, the DMAR unit is
 978                        bypassed by not enabling DMAR with this option. In
 979                        this case, gfx device will use physical address for
 980                        DMA.
 981                forcedac [x86_64]
 982                        With this option iommu will not optimize to look
 983                        for io virtual address below 32 bit forcing dual
 984                        address cycle on pci bus for cards supporting greater
 985                        than 32 bit addressing. The default is to look
 986                        for translation below 32 bit and if not available
 987                        then look in the higher range.
 988                strict [Default Off]
 989                        With this option on every unmap_single operation will
 990                        result in a hardware IOTLB flush operation as opposed
 991                        to batching them for performance.
 992
 993        intremap=       [X86-64, Intel-IOMMU]
 994                        Format: { on (default) | off | nosid }
 995                        on      enable Interrupt Remapping (default)
 996                        off     disable Interrupt Remapping
 997                        nosid   disable Source ID checking
 998
 999        inttest=        [IA64]
1000
1001        iomem=          Disable strict checking of access to MMIO memory
1002                strict  regions from userspace.
1003                relaxed
1004
1005        iommu=          [x86]
1006                off
1007                force
1008                noforce
1009                biomerge
1010                panic
1011                nopanic
1012                merge
1013                nomerge
1014                forcesac
1015                soft
1016                pt      [x86, IA64]
1017
1018        io7=            [HW] IO7 for Marvel based alpha systems
1019                        See comment before marvel_specify_io7 in
1020                        arch/alpha/kernel/core_marvel.c.
1021
1022        io_delay=       [X86] I/O delay method
1023                0x80
1024                        Standard port 0x80 based delay
1025                0xed
1026                        Alternate port 0xed based delay (needed on some systems)
1027                udelay
1028                        Simple two microseconds delay
1029                none
1030                        No delay
1031
1032        ip=             [IP_PNP]
1033                        See Documentation/filesystems/nfs/nfsroot.txt.
1034
1035        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1036                        See comment before ip2_setup() in
1037                        drivers/char/ip2/ip2base.c.
1038
1039        irqfixup        [HW]
1040                        When an interrupt is not handled search all handlers
1041                        for it. Intended to get systems with badly broken
1042                        firmware running.
1043
1044        irqpoll         [HW]
1045                        When an interrupt is not handled search all handlers
1046                        for it. Also check all handlers each timer
1047                        interrupt. Intended to get systems with badly broken
1048                        firmware running.
1049
1050        isapnp=         [ISAPNP]
1051                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1052
1053        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1054                        Format:
1055                        <cpu number>,...,<cpu number>
1056                        or
1057                        <cpu number>-<cpu number>
1058                        (must be a positive range in ascending order)
1059                        or a mixture
1060                        <cpu number>,...,<cpu number>-<cpu number>
1061
1062                        This option can be used to specify one or more CPUs
1063                        to isolate from the general SMP balancing and scheduling
1064                        algorithms. You can move a process onto or off an
1065                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1066                        <cpu number> begins at 0 and the maximum value is
1067                        "number of CPUs in system - 1".
1068
1069                        This option is the preferred way to isolate CPUs. The
1070                        alternative -- manually setting the CPU mask of all
1071                        tasks in the system -- can cause problems and
1072                        suboptimal load balancer performance.
1073
1074        iucv=           [HW,NET]
1075
1076        js=             [HW,JOY] Analog joystick
1077                        See Documentation/input/joystick.txt.
1078
1079        keepinitrd      [HW,ARM]
1080
1081        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1082                        specifies the amount of memory usable by the kernel
1083                        for non-movable allocations.  The requested amount is
1084                        spread evenly throughout all nodes in the system. The
1085                        remaining memory in each node is used for Movable
1086                        pages. In the event, a node is too small to have both
1087                        kernelcore and Movable pages, kernelcore pages will
1088                        take priority and other nodes will have a larger number
1089                        of kernelcore pages.  The Movable zone is used for the
1090                        allocation of pages that may be reclaimed or moved
1091                        by the page migration subsystem.  This means that
1092                        HugeTLB pages may not be allocated from this zone.
1093                        Note that allocations like PTEs-from-HighMem still
1094                        use the HighMem zone if it exists, and the Normal
1095                        zone if it does not.
1096
1097        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1098                        Format: <Controller#>[,poll interval]
1099                        The controller # is the number of the ehci usb debug
1100                        port as it is probed via PCI.  The poll interval is
1101                        optional and is the number seconds in between
1102                        each poll cycle to the debug port in case you need
1103                        the functionality for interrupting the kernel with
1104                        gdb or control-c on the dbgp connection.  When
1105                        not using this parameter you use sysrq-g to break into
1106                        the kernel debugger.
1107
1108        kgdboc=         [KGDB,HW] kgdb over consoles.
1109                        Requires a tty driver that supports console polling,
1110                        or a supported polling keyboard driver (non-usb).
1111                         Serial only format: <serial_device>[,baud]
1112                         keyboard only format: kbd
1113                         keyboard and serial format: kbd,<serial_device>[,baud]
1114                        Optional Kernel mode setting:
1115                         kms, kbd format: kms,kbd
1116                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1117
1118        kgdbwait        [KGDB] Stop kernel execution and enter the
1119                        kernel debugger at the earliest opportunity.
1120
1121        kmac=           [MIPS] korina ethernet MAC address.
1122                        Configure the RouterBoard 532 series on-chip
1123                        Ethernet adapter MAC address.
1124
1125        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1126                        Valid arguments: on, off
1127                        Default: on
1128
1129        kstack=N        [X86] Print N words from the kernel stack
1130                        in oops dumps.
1131
1132        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1133                        Default is 0 (don't ignore, but inject #GP)
1134
1135        kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1136                        Default is 1 (enabled)
1137
1138        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
1139                        KVM MMU at runtime.
1140                        Default is 0 (off)
1141
1142        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1143                        Default is 1 (enabled)
1144
1145        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1146                        for all guests.
1147                        Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1148
1149        kvm-intel.bypass_guest_pf=
1150                        [KVM,Intel] Disables bypassing of guest page faults
1151                        on Intel chips. Default is 1 (enabled)
1152
1153        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1154                        (virtualized MMU) support on capable Intel chips.
1155                        Default is 1 (enabled)
1156
1157        kvm-intel.emulate_invalid_guest_state=
1158                        [KVM,Intel] Enable emulation of invalid guest states
1159                        Default is 0 (disabled)
1160
1161        kvm-intel.flexpriority=
1162                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1163                        Default is 1 (enabled)
1164
1165        kvm-intel.unrestricted_guest=
1166                        [KVM,Intel] Disable unrestricted guest feature
1167                        (virtualized real and unpaged mode) on capable
1168                        Intel chips. Default is 1 (enabled)
1169
1170        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1171                        feature (tagged TLBs) on capable Intel chips.
1172                        Default is 1 (enabled)
1173
1174        l2cr=           [PPC]
1175
1176        l3cr=           [PPC]
1177
1178        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1179                        disabled it.
1180
1181        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1182                        in C2 power state.
1183
1184        libata.dma=     [LIBATA] DMA control
1185                        libata.dma=0      Disable all PATA and SATA DMA
1186                        libata.dma=1      PATA and SATA Disk DMA only
1187                        libata.dma=2      ATAPI (CDROM) DMA only
1188                        libata.dma=4      Compact Flash DMA only 
1189                        Combinations also work, so libata.dma=3 enables DMA
1190                        for disks and CDROMs, but not CFs.
1191        
1192        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1193                        libata.ignore_hpa=0       keep BIOS limits (default)
1194                        libata.ignore_hpa=1       ignore limits, using full disk
1195
1196        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1197                        when set.
1198                        Format: <int>
1199
1200        libata.force=   [LIBATA] Force configurations.  The format is comma
1201                        separated list of "[ID:]VAL" where ID is
1202                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1203                        matching port, link or device.  Basically, it matches
1204                        the ATA ID string printed on console by libata.  If
1205                        the whole ID part is omitted, the last PORT and DEVICE
1206                        values are used.  If ID hasn't been specified yet, the
1207                        configuration applies to all ports, links and devices.
1208
1209                        If only DEVICE is omitted, the parameter applies to
1210                        the port and all links and devices behind it.  DEVICE
1211                        number of 0 either selects the first device or the
1212                        first fan-out link behind PMP device.  It does not
1213                        select the host link.  DEVICE number of 15 selects the
1214                        host link and device attached to it.
1215
1216                        The VAL specifies the configuration to force.  As long
1217                        as there's no ambiguity shortcut notation is allowed.
1218                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1219                        The following configurations can be forced.
1220
1221                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1222                          Any ID with matching PORT is used.
1223
1224                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1225
1226                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1227                          udma[/][16,25,33,44,66,100,133] notation is also
1228                          allowed.
1229
1230                        * [no]ncq: Turn on or off NCQ.
1231
1232                        * nohrst, nosrst, norst: suppress hard, soft
1233                          and both resets.
1234
1235                        * dump_id: dump IDENTIFY data.
1236
1237                        If there are multiple matching configurations changing
1238                        the same attribute, the last one is used.
1239
1240        memblock=debug  [KNL] Enable memblock debug messages.
1241
1242        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1243                        See Documentation/blockdev/ramdisk.txt.
1244
1245        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1246                        Format: <integer>
1247
1248        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1249                        Format: <integer>
1250
1251        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1252                        Format: <integer>
1253
1254        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1255                        Format: <integer>
1256
1257        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1258                        Format: <irq>
1259
1260        loglevel=       All Kernel Messages with a loglevel smaller than the
1261                        console loglevel will be printed to the console. It can
1262                        also be changed with klogd or other programs. The
1263                        loglevels are defined as follows:
1264
1265                        0 (KERN_EMERG)          system is unusable
1266                        1 (KERN_ALERT)          action must be taken immediately
1267                        2 (KERN_CRIT)           critical conditions
1268                        3 (KERN_ERR)            error conditions
1269                        4 (KERN_WARNING)        warning conditions
1270                        5 (KERN_NOTICE)         normal but significant condition
1271                        6 (KERN_INFO)           informational
1272                        7 (KERN_DEBUG)          debug-level messages
1273
1274        log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
1275                        in bytes.  n must be a power of two.  The default
1276                        size is set in the kernel config file.
1277
1278        logo.nologo     [FB] Disables display of the built-in Linux logo.
1279                        This may be used to provide more screen space for
1280                        kernel log messages and is useful when debugging
1281                        kernel boot problems.
1282
1283        lp=0            [LP]    Specify parallel ports to use, e.g,
1284        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1285        lp=reset                first parallel port). 'lp=0' disables the
1286        lp=auto                 printer driver. 'lp=reset' (which can be
1287                                specified in addition to the ports) causes
1288                                attached printers to be reset. Using
1289                                lp=port1,port2,... specifies the parallel ports
1290                                to associate lp devices with, starting with
1291                                lp0. A port specification may be 'none' to skip
1292                                that lp device, or a parport name such as
1293                                'parport0'. Specifying 'lp=auto' instead of a
1294                                port specification list means that device IDs
1295                                from each port should be examined, to see if
1296                                an IEEE 1284-compliant printer is attached; if
1297                                so, the driver will manage that printer.
1298                                See also header of drivers/char/lp.c.
1299
1300        lpj=n           [KNL]
1301                        Sets loops_per_jiffy to given constant, thus avoiding
1302                        time-consuming boot-time autodetection (up to 250 ms per
1303                        CPU). 0 enables autodetection (default). To determine
1304                        the correct value for your kernel, boot with normal
1305                        autodetection and see what value is printed. Note that
1306                        on SMP systems the preset will be applied to all CPUs,
1307                        which is likely to cause problems if your CPUs need
1308                        significantly divergent settings. An incorrect value
1309                        will cause delays in the kernel to be wrong, leading to
1310                        unpredictable I/O errors and other breakage. Although
1311                        unlikely, in the extreme case this might damage your
1312                        hardware.
1313
1314        ltpc=           [NET]
1315                        Format: <io>,<irq>,<dma>
1316
1317        machvec=        [IA64] Force the use of a particular machine-vector
1318                        (machvec) in a generic kernel.
1319                        Example: machvec=hpzx1_swiotlb
1320
1321        machtype=       [Loongson] Share the same kernel image file between different
1322                         yeeloong laptop.
1323                        Example: machtype=lemote-yeeloong-2f-7inch
1324
1325        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1326                        than or equal to this physical address is ignored.
1327
1328        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1329                        should make use of.  maxcpus=n : n >= 0 limits the
1330                        kernel to using 'n' processors.  n=0 is a special case,
1331                        it is equivalent to "nosmp", which also disables
1332                        the IO APIC.
1333
1334        max_loop=       [LOOP] Maximum number of loopback devices that can
1335                        be mounted
1336                        Format: <1-256>
1337
1338        mcatest=        [IA-64]
1339
1340        mce             [X86-32] Machine Check Exception
1341
1342        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1343
1344        md=             [HW] RAID subsystems devices and level
1345                        See Documentation/md.txt.
1346
1347        mdacon=         [MDA]
1348                        Format: <first>,<last>
1349                        Specifies range of consoles to be captured by the MDA.
1350
1351        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1352                        Amount of memory to be used when the kernel is not able
1353                        to see the whole system memory or for test.
1354                        [X86-32] Use together with memmap= to avoid physical
1355                        address space collisions. Without memmap= PCI devices
1356                        could be placed at addresses belonging to unused RAM.
1357
1358        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1359                        memory.
1360
1361        memchunk=nn[KMG]
1362                        [KNL,SH] Allow user to override the default size for
1363                        per-device physically contiguous DMA buffers.
1364
1365        memmap=exactmap [KNL,X86] Enable setting of an exact
1366                        E820 memory map, as specified by the user.
1367                        Such memmap=exactmap lines can be constructed based on
1368                        BIOS output or other requirements. See the memmap=nn@ss
1369                        option description.
1370
1371        memmap=nn[KMG]@ss[KMG]
1372                        [KNL] Force usage of a specific region of memory
1373                        Region of memory to be used, from ss to ss+nn.
1374
1375        memmap=nn[KMG]#ss[KMG]
1376                        [KNL,ACPI] Mark specific memory as ACPI data.
1377                        Region of memory to be used, from ss to ss+nn.
1378
1379        memmap=nn[KMG]$ss[KMG]
1380                        [KNL,ACPI] Mark specific memory as reserved.
1381                        Region of memory to be used, from ss to ss+nn.
1382                        Example: Exclude memory from 0x18690000-0x1869ffff
1383                                 memmap=64K$0x18690000
1384                                 or
1385                                 memmap=0x10000$0x18690000
1386
1387        memory_corruption_check=0/1 [X86]
1388                        Some BIOSes seem to corrupt the first 64k of
1389                        memory when doing things like suspend/resume.
1390                        Setting this option will scan the memory
1391                        looking for corruption.  Enabling this will
1392                        both detect corruption and prevent the kernel
1393                        from using the memory being corrupted.
1394                        However, its intended as a diagnostic tool; if
1395                        repeatable BIOS-originated corruption always
1396                        affects the same memory, you can use memmap=
1397                        to prevent the kernel from using that memory.
1398
1399        memory_corruption_check_size=size [X86]
1400                        By default it checks for corruption in the low
1401                        64k, making this memory unavailable for normal
1402                        use.  Use this parameter to scan for
1403                        corruption in more or less memory.
1404
1405        memory_corruption_check_period=seconds [X86]
1406                        By default it checks for corruption every 60
1407                        seconds.  Use this parameter to check at some
1408                        other rate.  0 disables periodic checking.
1409
1410        memtest=        [KNL,X86] Enable memtest
1411                        Format: <integer>
1412                        default : 0 <disable>
1413                        Specifies the number of memtest passes to be
1414                        performed. Each pass selects another test
1415                        pattern from a given set of patterns. Memtest
1416                        fills the memory with this pattern, validates
1417                        memory contents and reserves bad memory
1418                        regions that are detected.
1419
1420        meye.*=         [HW] Set MotionEye Camera parameters
1421                        See Documentation/video4linux/meye.txt.
1422
1423        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1424                        Multi-Function General Purpose Timers on AMD Geode
1425                        platforms.
1426
1427        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1428                        the BIOS has incorrectly applied a workaround. TinyBIOS
1429                        version 0.98 is known to be affected, 0.99 fixes the
1430                        problem by letting the user disable the workaround.
1431
1432        mga=            [HW,DRM]
1433
1434        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1435                        physical address is ignored.
1436
1437        mini2440=       [ARM,HW,KNL]
1438                        Format:[0..2][b][c][t]
1439                        Default: "0tb"
1440                        MINI2440 configuration specification:
1441                        0 - The attached screen is the 3.5" TFT
1442                        1 - The attached screen is the 7" TFT
1443                        2 - The VGA Shield is attached (1024x768)
1444                        Leaving out the screen size parameter will not load
1445                        the TFT driver, and the framebuffer will be left
1446                        unconfigured.
1447                        b - Enable backlight. The TFT backlight pin will be
1448                        linked to the kernel VESA blanking code and a GPIO
1449                        LED. This parameter is not necessary when using the
1450                        VGA shield.
1451                        c - Enable the s3c camera interface.
1452                        t - Reserved for enabling touchscreen support. The
1453                        touchscreen support is not enabled in the mainstream
1454                        kernel as of 2.6.30, a preliminary port can be found
1455                        in the "bleeding edge" mini2440 support kernel at
1456                        http://repo.or.cz/w/linux-2.6/mini2440.git
1457
1458        mminit_loglevel=
1459                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1460                        parameter allows control of the logging verbosity for
1461                        the additional memory initialisation checks. A value
1462                        of 0 disables mminit logging and a level of 4 will
1463                        log everything. Information is printed at KERN_DEBUG
1464                        so loglevel=8 may also need to be specified.
1465
1466        mousedev.tap_time=
1467                        [MOUSE] Maximum time between finger touching and
1468                        leaving touchpad surface for touch to be considered
1469                        a tap and be reported as a left button click (for
1470                        touchpads working in absolute mode only).
1471                        Format: <msecs>
1472        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1473                        reporting absolute coordinates, such as tablets
1474        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1475                        reporting absolute coordinates, such as tablets
1476
1477        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1478                        is similar to kernelcore except it specifies the
1479                        amount of memory used for migratable allocations.
1480                        If both kernelcore and movablecore is specified,
1481                        then kernelcore will be at *least* the specified
1482                        value but may be more. If movablecore on its own
1483                        is specified, the administrator must be careful
1484                        that the amount of memory usable for all allocations
1485                        is not too small.
1486
1487        MTD_Partition=  [MTD]
1488                        Format: <name>,<region-number>,<size>,<offset>
1489
1490        MTD_Region=     [MTD] Format:
1491                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1492
1493        mtdparts=       [MTD]
1494                        See drivers/mtd/cmdlinepart.c.
1495
1496        multitce=off    [PPC]  This parameter disables the use of the pSeries
1497                        firmware feature for updating multiple TCE entries
1498                        at a time.
1499
1500        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1501
1502                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1503
1504                        boundary - index of last SLC block on Flex-OneNAND.
1505                                   The remaining blocks are configured as MLC blocks.
1506                        lock     - Configure if Flex-OneNAND boundary should be locked.
1507                                   Once locked, the boundary cannot be changed.
1508                                   1 indicates lock status, 0 indicates unlock status.
1509
1510        mtdset=         [ARM]
1511                        ARM/S3C2412 JIVE boot control
1512
1513                        See arch/arm/mach-s3c2412/mach-jive.c
1514
1515        mtouchusb.raw_coordinates=
1516                        [HW] Make the MicroTouch USB driver use raw coordinates
1517                        ('y', default) or cooked coordinates ('n')
1518
1519        mtrr_chunk_size=nn[KMG] [X86]
1520                        used for mtrr cleanup. It is largest continuous chunk
1521                        that could hold holes aka. UC entries.
1522
1523        mtrr_gran_size=nn[KMG] [X86]
1524                        Used for mtrr cleanup. It is granularity of mtrr block.
1525                        Default is 1.
1526                        Large value could prevent small alignment from
1527                        using up MTRRs.
1528
1529        mtrr_spare_reg_nr=n [X86]
1530                        Format: <integer>
1531                        Range: 0,7 : spare reg number
1532                        Default : 1
1533                        Used for mtrr cleanup. It is spare mtrr entries number.
1534                        Set to 2 or more if your graphical card needs more.
1535
1536        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1537
1538        netdev=         [NET] Network devices parameters
1539                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1540                        Note that mem_start is often overloaded to mean
1541                        something different and driver-specific.
1542                        This usage is only documented in each driver source
1543                        file if at all.
1544
1545        nf_conntrack.acct=
1546                        [NETFILTER] Enable connection tracking flow accounting
1547                        0 to disable accounting
1548                        1 to enable accounting
1549                        Default value is 0.
1550
1551        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
1552                        See Documentation/filesystems/nfs/nfsroot.txt.
1553
1554        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1555                        See Documentation/filesystems/nfs/nfsroot.txt.
1556
1557        nfsrootdebug    [NFS] enable nfsroot debugging messages.
1558                        See Documentation/filesystems/nfs/nfsroot.txt.
1559
1560        nfs.callback_tcpport=
1561                        [NFS] set the TCP port on which the NFSv4 callback
1562                        channel should listen.
1563
1564        nfs.cache_getent=
1565                        [NFS] sets the pathname to the program which is used
1566                        to update the NFS client cache entries.
1567
1568        nfs.cache_getent_timeout=
1569                        [NFS] sets the timeout after which an attempt to
1570                        update a cache entry is deemed to have failed.
1571
1572        nfs.idmap_cache_timeout=
1573                        [NFS] set the maximum lifetime for idmapper cache
1574                        entries.
1575
1576        nfs.enable_ino64=
1577                        [NFS] enable 64-bit inode numbers.
1578                        If zero, the NFS client will fake up a 32-bit inode
1579                        number for the readdir() and stat() syscalls instead
1580                        of returning the full 64-bit number.
1581                        The default is to return 64-bit inode numbers.
1582
1583        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1584                        when a NMI is triggered.
1585                        Format: [state][,regs][,debounce][,die]
1586
1587        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1588                        Format: [panic,][num]
1589                        Valid num: 0
1590                        0 - turn nmi_watchdog off
1591                        When panic is specified, panic when an NMI watchdog
1592                        timeout occurs.
1593                        This is useful when you use a panic=... timeout and
1594                        need the box quickly up again.
1595
1596        netpoll.carrier_timeout=
1597                        [NET] Specifies amount of time (in seconds) that
1598                        netpoll should wait for a carrier. By default netpoll
1599                        waits 4 seconds.
1600
1601        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1602                        emulation library even if a 387 maths coprocessor
1603                        is present.
1604
1605        no_console_suspend
1606                        [HW] Never suspend the console
1607                        Disable suspending of consoles during suspend and
1608                        hibernate operations.  Once disabled, debugging
1609                        messages can reach various consoles while the rest
1610                        of the system is being put to sleep (ie, while
1611                        debugging driver suspend/resume hooks).  This may
1612                        not work reliably with all consoles, but is known
1613                        to work with serial and VGA consoles.
1614
1615        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1616                        caches in the slab allocator.  Saves per-node memory,
1617                        but will impact performance.
1618
1619        noalign         [KNL,ARM]
1620
1621        noapic          [SMP,APIC] Tells the kernel to not make use of any
1622                        IOAPICs that may be present in the system.
1623
1624        noautogroup     Disable scheduler automatic task group creation.
1625
1626        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1627                        on "Classic" PPC cores.
1628
1629        nocache         [ARM]
1630
1631        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1632
1633        nodelayacct     [KNL] Disable per-task delay accounting
1634
1635        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1636
1637        nodsp           [SH] Disable hardware DSP at boot time.
1638
1639        noefi           [X86] Disable EFI runtime services support.
1640
1641        noexec          [IA-64]
1642
1643        noexec          [X86]
1644                        On X86-32 available only on PAE configured kernels.
1645                        noexec=on: enable non-executable mappings (default)
1646                        noexec=off: disable non-executable mappings
1647
1648        noexec32        [X86-64]
1649                        This affects only 32-bit executables.
1650                        noexec32=on: enable non-executable mappings (default)
1651                                read doesn't imply executable mappings
1652                        noexec32=off: disable non-executable mappings
1653                                read implies executable mappings
1654
1655        nofpu           [SH] Disable hardware FPU at boot time.
1656
1657        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1658                        register save and restore. The kernel will only save
1659                        legacy floating-point registers on task switch.
1660
1661        noxsave         [BUGS=X86] Disables x86 extended register state save
1662                        and restore using xsave. The kernel will fallback to
1663                        enabling legacy floating-point and sse state.
1664
1665        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1666                        wfi(ARM) instruction doesn't work correctly and not to
1667                        use it. This is also useful when using JTAG debugger.
1668
1669        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1670                        instruction doesn't work correctly and not to
1671                        use it.
1672
1673        no_file_caps    Tells the kernel not to honor file capabilities.  The
1674                        only way then for a file to be executed with privilege
1675                        is to be setuid root or executed by root.
1676
1677        nohalt          [IA-64] Tells the kernel not to use the power saving
1678                        function PAL_HALT_LIGHT when idle. This increases
1679                        power-consumption. On the positive side, it reduces
1680                        interrupt wake-up latency, which may improve performance
1681                        in certain environments such as networked servers or
1682                        real-time systems.
1683
1684        nohz=           [KNL] Boottime enable/disable dynamic ticks
1685                        Valid arguments: on, off
1686                        Default: on
1687
1688        noiotrap        [SH] Disables trapped I/O port accesses.
1689
1690        noirqdebug      [X86-32] Disables the code which attempts to detect and
1691                        disable unhandled interrupt sources.
1692
1693        no_timer_check  [X86,APIC] Disables the code which tests for
1694                        broken timer IRQ sources.
1695
1696        noisapnp        [ISAPNP] Disables ISA PnP code.
1697
1698        noinitrd        [RAM] Tells the kernel not to load any configured
1699                        initial RAM disk.
1700
1701        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1702                        remapping.
1703                        [Deprecated - use intremap=off]
1704
1705        nointroute      [IA-64]
1706
1707        nojitter        [IA64] Disables jitter checking for ITC timers.
1708
1709        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
1710
1711        no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
1712                        fault handling.
1713
1714        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1715
1716        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1717
1718        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1719                        lowmem mapping on PPC40x.
1720
1721        nomca           [IA-64] Disable machine check abort handling
1722
1723        nomce           [X86-32] Machine Check Exception
1724
1725        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1726                        Timer usage (for AMD Geode machines).
1727
1728        nopat           [X86] Disable PAT (page attribute table extension of
1729                        pagetables) support.
1730
1731        norandmaps      Don't use address space randomization.  Equivalent to
1732                        echo 0 > /proc/sys/kernel/randomize_va_space
1733
1734        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1735
1736        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1737                        with UP alternatives
1738
1739        noresidual      [PPC] Don't use residual data on PReP machines.
1740
1741        noresume        [SWSUSP] Disables resume and restores original swap
1742                        space.
1743
1744        no-scroll       [VGA] Disables scrollback.
1745                        This is required for the Braillex ib80-piezo Braille
1746                        reader made by F.H. Papenmeier (Germany).
1747
1748        nosbagart       [IA-64]
1749
1750        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1751
1752        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1753                        and disable the IO APIC.  legacy for "maxcpus=0".
1754
1755        nosoftlockup    [KNL] Disable the soft-lockup detector.
1756
1757        noswapaccount   [KNL] Disable accounting of swap in memory resource
1758                        controller. (See Documentation/cgroups/memory.txt)
1759
1760        nosync          [HW,M68K] Disables sync negotiation for all devices.
1761
1762        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1763
1764        nousb           [USB] Disable the USB subsystem
1765
1766        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
1767
1768        nowb            [ARM]
1769
1770        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1771
1772        nptcg=          [IA64] Override max number of concurrent global TLB
1773                        purges which is reported from either PAL_VM_SUMMARY or
1774                        SAL PALO.
1775
1776        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
1777                        could support.  nr_cpus=n : n >= 1 limits the kernel to
1778                        supporting 'n' processors. Later in runtime you can not
1779                        use hotplug cpu feature to put more cpu back to online.
1780                        just like you compile the kernel NR_CPUS=n
1781
1782        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1783
1784        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1785                        one of ['zone', 'node', 'default'] can be specified
1786                        This can be set from sysctl after boot.
1787                        See Documentation/sysctl/vm.txt for details.
1788
1789        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1790                        See Documentation/debugging-via-ohci1394.txt for more
1791                        info.
1792
1793        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1794                        Rather than timing out after 20 ms if an EC
1795                        command is not properly ACKed, override the length
1796                        of the timeout.  We have interrupts disabled while
1797                        waiting for the ACK, so if this is set too high
1798                        interrupts *may* be lost!
1799
1800        omap_mux=       [OMAP] Override bootloader pin multiplexing.
1801                        Format: <mux_mode0.mode_name=value>...
1802                        For example, to override I2C bus2:
1803                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1804
1805        oprofile.timer= [HW]
1806                        Use timer interrupt instead of performance counters
1807
1808        oprofile.cpu_type=      Force an oprofile cpu type
1809                        This might be useful if you have an older oprofile
1810                        userland or if you want common events.
1811                        Format: { arch_perfmon }
1812                        arch_perfmon: [X86] Force use of architectural
1813                                perfmon on Intel CPUs instead of the
1814                                CPU specific event set.
1815
1816        OSS             [HW,OSS]
1817                        See Documentation/sound/oss/oss-parameters.txt
1818
1819        panic=          [KNL] Kernel behaviour on panic
1820                        Format: <timeout>
1821
1822        parkbd.port=    [HW] Parallel port number the keyboard adapter is
1823                        connected to, default is 0.
1824                        Format: <parport#>
1825        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1826                        0 for XT, 1 for AT (default is AT).
1827                        Format: <mode>
1828
1829        parport=        [HW,PPT] Specify parallel ports. 0 disables.
1830                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1831                        Use 'auto' to force the driver to use any
1832                        IRQ/DMA settings detected (the default is to
1833                        ignore detected IRQ/DMA settings because of
1834                        possible conflicts). You can specify the base
1835                        address, IRQ, and DMA settings; IRQ and DMA
1836                        should be numbers, or 'auto' (for using detected
1837                        settings on that particular port), or 'nofifo'
1838                        (to avoid using a FIFO even if it is detected).
1839                        Parallel ports are assigned in the order they
1840                        are specified on the command line, starting
1841                        with parport0.
1842
1843        parport_init_mode=      [HW,PPT]
1844                        Configure VIA parallel port to operate in
1845                        a specific mode. This is necessary on Pegasos
1846                        computer where firmware has no options for setting
1847                        up parallel port mode and sets it to spp.
1848                        Currently this function knows 686a and 8231 chips.
1849                        Format: [spp|ps2|epp|ecp|ecpepp]
1850
1851        pause_on_oops=
1852                        Halt all CPUs after the first oops has been printed for
1853                        the specified number of seconds.  This is to be used if
1854                        your oopses keep scrolling off the screen.
1855
1856        pcbit=          [HW,ISDN]
1857
1858        pcd.            [PARIDE]
1859                        See header of drivers/block/paride/pcd.c.
1860                        See also Documentation/blockdev/paride.txt.
1861
1862        pci=option[,option...]  [PCI] various PCI subsystem options:
1863                earlydump       [X86] dump PCI config space before the kernel
1864                                changes anything
1865                off             [X86] don't probe for the PCI bus
1866                bios            [X86-32] force use of PCI BIOS, don't access
1867                                the hardware directly. Use this if your machine
1868                                has a non-standard PCI host bridge.
1869                nobios          [X86-32] disallow use of PCI BIOS, only direct
1870                                hardware access methods are allowed. Use this
1871                                if you experience crashes upon bootup and you
1872                                suspect they are caused by the BIOS.
1873                conf1           [X86] Force use of PCI Configuration
1874                                Mechanism 1.
1875                conf2           [X86] Force use of PCI Configuration
1876                                Mechanism 2.
1877                noaer           [PCIE] If the PCIEAER kernel config parameter is
1878                                enabled, this kernel boot option can be used to
1879                                disable the use of PCIE advanced error reporting.
1880                nodomains       [PCI] Disable support for multiple PCI
1881                                root domains (aka PCI segments, in ACPI-speak).
1882                nommconf        [X86] Disable use of MMCONFIG for PCI
1883                                Configuration
1884                check_enable_amd_mmconf [X86] check for and enable
1885                                properly configured MMIO access to PCI
1886                                config space on AMD family 10h CPU
1887                nomsi           [MSI] If the PCI_MSI kernel config parameter is
1888                                enabled, this kernel boot option can be used to
1889                                disable the use of MSI interrupts system-wide.
1890                noioapicquirk   [APIC] Disable all boot interrupt quirks.
1891                                Safety option to keep boot IRQs enabled. This
1892                                should never be necessary.
1893                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
1894                                primary IO-APIC for bridges that cannot disable
1895                                boot IRQs. This fixes a source of spurious IRQs
1896                                when the system masks IRQs.
1897                noioapicreroute [APIC] Disable workaround that uses the
1898                                boot IRQ equivalent of an IRQ that connects to
1899                                a chipset where boot IRQs cannot be disabled.
1900                                The opposite of ioapicreroute.
1901                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
1902                                routing table. These calls are known to be buggy
1903                                on several machines and they hang the machine
1904                                when used, but on other computers it's the only
1905                                way to get the interrupt routing table. Try
1906                                this option if the kernel is unable to allocate
1907                                IRQs or discover secondary PCI buses on your
1908                                motherboard.
1909                rom             [X86] Assign address space to expansion ROMs.
1910                                Use with caution as certain devices share
1911                                address decoders between ROMs and other
1912                                resources.
1913                norom           [X86] Do not assign address space to
1914                                expansion ROMs that do not already have
1915                                BIOS assigned address ranges.
1916                nobar           [X86] Do not assign address space to the
1917                                BARs that weren't assigned by the BIOS.
1918                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
1919                                assigned automatically to PCI devices. You can
1920                                make the kernel exclude IRQs of your ISA cards
1921                                this way.
1922                pirqaddr=0xAAAAA        [X86] Specify the physical address
1923                                of the PIRQ table (normally generated
1924                                by the BIOS) if it is outside the
1925                                F0000h-100000h range.
1926                lastbus=N       [X86] Scan all buses thru bus #N. Can be
1927                                useful if the kernel is unable to find your
1928                                secondary buses and you want to tell it
1929                                explicitly which ones they are.
1930                assign-busses   [X86] Always assign all PCI bus
1931                                numbers ourselves, overriding
1932                                whatever the firmware may have done.
1933                usepirqmask     [X86] Honor the possible IRQ mask stored
1934                                in the BIOS $PIR table. This is needed on
1935                                some systems with broken BIOSes, notably
1936                                some HP Pavilion N5400 and Omnibook XE3
1937                                notebooks. This will have no effect if ACPI
1938                                IRQ routing is enabled.
1939                noacpi          [X86] Do not use ACPI for IRQ routing
1940                                or for PCI scanning.
1941                use_crs         [X86] Use PCI host bridge window information
1942                                from ACPI.  On BIOSes from 2008 or later, this
1943                                is enabled by default.  If you need to use this,
1944                                please report a bug.
1945                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
1946                                If you need to use this, please report a bug.
1947                routeirq        Do IRQ routing for all PCI devices.
1948                                This is normally done in pci_enable_device(),
1949                                so this option is a temporary workaround
1950                                for broken drivers that don't call it.
1951                skip_isa_align  [X86] do not align io start addr, so can
1952                                handle more pci cards
1953                firmware        [ARM] Do not re-enumerate the bus but instead
1954                                just use the configuration from the
1955                                bootloader. This is currently used on
1956                                IXP2000 systems where the bus has to be
1957                                configured a certain way for adjunct CPUs.
1958                noearly         [X86] Don't do any early type 1 scanning.
1959                                This might help on some broken boards which
1960                                machine check when some devices' config space
1961                                is read. But various workarounds are disabled
1962                                and some IOMMU drivers will not work.
1963                bfsort          Sort PCI devices into breadth-first order.
1964                                This sorting is done to get a device
1965                                order compatible with older (<= 2.4) kernels.
1966                nobfsort        Don't sort PCI devices into breadth-first order.
1967                cbiosize=nn[KMG]        The fixed amount of bus space which is
1968                                reserved for the CardBus bridge's IO window.
1969                                The default value is 256 bytes.
1970                cbmemsize=nn[KMG]       The fixed amount of bus space which is
1971                                reserved for the CardBus bridge's memory
1972                                window. The default value is 64 megabytes.
1973                resource_alignment=
1974                                Format:
1975                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1976                                Specifies alignment and device to reassign
1977                                aligned memory resources.
1978                                If <order of align> is not specified,
1979                                PAGE_SIZE is used as alignment.
1980                                PCI-PCI bridge can be specified, if resource
1981                                windows need to be expanded.
1982                ecrc=           Enable/disable PCIe ECRC (transaction layer
1983                                end-to-end CRC checking).
1984                                bios: Use BIOS/firmware settings. This is the
1985                                the default.
1986                                off: Turn ECRC off
1987                                on: Turn ECRC on.
1988
1989        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
1990                        Management.
1991                off     Disable ASPM.
1992                force   Enable ASPM even on devices that claim not to support it.
1993                        WARNING: Forcing ASPM on may cause system lockups.
1994
1995        pcie_ports=     [PCIE] PCIe ports handling:
1996                auto    Ask the BIOS whether or not to use native PCIe services
1997                        associated with PCIe ports (PME, hot-plug, AER).  Use
1998                        them only if that is allowed by the BIOS.
1999                native  Use native PCIe services associated with PCIe ports
2000                        unconditionally.
2001                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2002                        ports driver.
2003
2004        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
2005                nomsi   Do not use MSI for native PCIe PME signaling (this makes
2006                        all PCIe root ports use INTx for all services).
2007
2008        pcmv=           [HW,PCMCIA] BadgePAD 4
2009
2010        pd.             [PARIDE]
2011                        See Documentation/blockdev/paride.txt.
2012
2013        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2014                        boot time.
2015                        Format: { 0 | 1 }
2016                        See arch/parisc/kernel/pdc_chassis.c
2017
2018        percpu_alloc=   Select which percpu first chunk allocator to use.
2019                        Currently supported values are "embed" and "page".
2020                        Archs may support subset or none of the selections.
2021                        See comments in mm/percpu.c for details on each
2022                        allocator.  This parameter is primarily for debugging
2023                        and performance comparison.
2024
2025        pf.             [PARIDE]
2026                        See Documentation/blockdev/paride.txt.
2027
2028        pg.             [PARIDE]
2029                        See Documentation/blockdev/paride.txt.
2030
2031        pirq=           [SMP,APIC] Manual mp-table setup
2032                        See Documentation/x86/i386/IO-APIC.txt.
2033
2034        plip=           [PPT,NET] Parallel port network link
2035                        Format: { parport<nr> | timid | 0 }
2036                        See also Documentation/parport.txt.
2037
2038        pmtmr=          [X86] Manual setup of pmtmr I/O Port. 
2039                        Override pmtimer IOPort with a hex value.
2040                        e.g. pmtmr=0x508
2041
2042        pnp.debug       [PNP]
2043                        Enable PNP debug messages.  This depends on the
2044                        CONFIG_PNP_DEBUG_MESSAGES option.
2045
2046        pnpacpi=        [ACPI]
2047                        { off }
2048
2049        pnpbios=        [ISAPNP]
2050                        { on | off | curr | res | no-curr | no-res }
2051
2052        pnp_reserve_irq=
2053                        [ISAPNP] Exclude IRQs for the autoconfiguration
2054
2055        pnp_reserve_dma=
2056                        [ISAPNP] Exclude DMAs for the autoconfiguration
2057
2058        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2059                        Ranges are in pairs (I/O port base and size).
2060
2061        pnp_reserve_mem=
2062                        [ISAPNP] Exclude memory regions for the
2063                        autoconfiguration.
2064                        Ranges are in pairs (memory base and size).
2065
2066        ports=          [IP_VS_FTP] IPVS ftp helper module
2067                        Default is 21.
2068                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2069                        may be specified.
2070                        Format: <port>,<port>....
2071
2072        print-fatal-signals=
2073                        [KNL] debug: print fatal signals
2074
2075                        If enabled, warn about various signal handling
2076                        related application anomalies: too many signals,
2077                        too many POSIX.1 timers, fatal signals causing a
2078                        coredump - etc.
2079
2080                        If you hit the warning due to signal overflow,
2081                        you might want to try "ulimit -i unlimited".
2082
2083                        default: off.
2084
2085        printk.time=    Show timing data prefixed to each printk message line
2086                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2087
2088        processor.max_cstate=   [HW,ACPI]
2089                        Limit processor to maximum C-state
2090                        max_cstate=9 overrides any DMI blacklist limit.
2091
2092        processor.nocst [HW,ACPI]
2093                        Ignore the _CST method to determine C-states,
2094                        instead using the legacy FADT method
2095
2096        profile=        [KNL] Enable kernel profiling via /proc/profile
2097                        Format: [schedule,]<number>
2098                        Param: "schedule" - profile schedule points.
2099                        Param: <number> - step/bucket size as a power of 2 for
2100                                statistical time based profiling.
2101                        Param: "sleep" - profile D-state sleeping (millisecs).
2102                                Requires CONFIG_SCHEDSTATS
2103                        Param: "kvm" - profile VM exits.
2104
2105        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2106                        before loading.
2107                        See Documentation/blockdev/ramdisk.txt.
2108
2109        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2110                        probe for; one of (bare|imps|exps|lifebook|any).
2111        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2112                        per second.
2113        psmouse.resetafter=     [HW,MOUSE]
2114                        Try to reset the device after so many bad packets
2115                        (0 = never).
2116        psmouse.resolution=
2117                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2118        psmouse.smartscroll=
2119                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2120                        0 = disabled, 1 = enabled (default).
2121
2122        pt.             [PARIDE]
2123                        See Documentation/blockdev/paride.txt.
2124
2125        pty.legacy_count=
2126                        [KNL] Number of legacy pty's. Overwrites compiled-in
2127                        default number.
2128
2129        quiet           [KNL] Disable most log messages
2130
2131        r128=           [HW,DRM]
2132
2133        raid=           [HW,RAID]
2134                        See Documentation/md.txt.
2135
2136        ramdisk_blocksize=      [RAM]
2137                        See Documentation/blockdev/ramdisk.txt.
2138
2139        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2140                        See Documentation/blockdev/ramdisk.txt.
2141
2142        rcupdate.blimit=        [KNL,BOOT]
2143                        Set maximum number of finished RCU callbacks to process
2144                        in one batch.
2145
2146        rcupdate.qhimark=       [KNL,BOOT]
2147                        Set threshold of queued
2148                        RCU callbacks over which batch limiting is disabled.
2149
2150        rcupdate.qlowmark=      [KNL,BOOT]
2151                        Set threshold of queued RCU callbacks below which
2152                        batch limiting is re-enabled.
2153
2154        rdinit=         [KNL]
2155                        Format: <full_path>
2156                        Run specified binary instead of /init from the ramdisk,
2157                        used for early userspace startup. See initrd.
2158
2159        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2160                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2161                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2162
2163        relax_domain_level=
2164                        [KNL, SMP] Set scheduler's default relax_domain_level.
2165                        See Documentation/cgroups/cpusets.txt.
2166
2167        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2168
2169        reservetop=     [X86-32]
2170                        Format: nn[KMG]
2171                        Reserves a hole at the top of the kernel virtual
2172                        address space.
2173
2174        reservelow=     [X86]
2175                        Format: nn[K]
2176                        Set the amount of memory to reserve for BIOS at
2177                        the bottom of the address space.
2178
2179        reset_devices   [KNL] Force drivers to reset the underlying device
2180                        during initialization.
2181
2182        resume=         [SWSUSP]
2183                        Specify the partition device for software suspend
2184
2185        resume_offset=  [SWSUSP]
2186                        Specify the offset from the beginning of the partition
2187                        given by "resume=" at which the swap header is located,
2188                        in <PAGE_SIZE> units (needed only for swap files).
2189                        See  Documentation/power/swsusp-and-swap-files.txt
2190
2191        hibernate=      [HIBERNATION]
2192                noresume        Don't check if there's a hibernation image
2193                                present during boot.
2194                nocompress      Don't compress/decompress hibernation images.
2195
2196        retain_initrd   [RAM] Keep initrd memory after extraction
2197
2198        rhash_entries=  [KNL,NET]
2199                        Set number of hash buckets for route cache
2200
2201        riscom8=        [HW,SERIAL]
2202                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2203
2204        ro              [KNL] Mount root device read-only on boot
2205
2206        root=           [KNL] Root filesystem
2207
2208        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2209                        mount the root filesystem
2210
2211        rootflags=      [KNL] Set root filesystem mount option string
2212
2213        rootfstype=     [KNL] Set root filesystem type
2214
2215        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2216                        Useful for devices that are detected asynchronously
2217                        (e.g. USB and MMC devices).
2218
2219        rw              [KNL] Mount root device read-write on boot
2220
2221        S               [KNL] Run init in single mode
2222
2223        sa1100ir        [NET]
2224                        See drivers/net/irda/sa1100_ir.c.
2225
2226        sbni=           [NET] Granch SBNI12 leased line adapter
2227
2228        sched_debug     [KNL] Enables verbose scheduler debug messages.
2229
2230        security=       [SECURITY] Choose a security module to enable at boot.
2231                        If this boot parameter is not specified, only the first
2232                        security module asking for security registration will be
2233                        loaded. An invalid security module name will be treated
2234                        as if no module has been chosen.
2235
2236        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2237                        Format: { "0" | "1" }
2238                        See security/selinux/Kconfig help text.
2239                        0 -- disable.
2240                        1 -- enable.
2241                        Default value is set via kernel config option.
2242                        If enabled at boot time, /selinux/disable can be used
2243                        later to disable prior to initial policy load.
2244
2245        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2246                        Format: { "0" | "1" }
2247                        See security/apparmor/Kconfig help text
2248                        0 -- disable.
2249                        1 -- enable.
2250                        Default value is set via kernel config option.
2251
2252        serialnumber    [BUGS=X86-32]
2253
2254        shapers=        [NET]
2255                        Maximal number of shapers.
2256
2257        show_msr=       [x86] show boot-time MSR settings
2258                        Format: { <integer> }
2259                        Show boot-time (BIOS-initialized) MSR settings.
2260                        The parameter means the number of CPUs to show,
2261                        for example 1 means boot CPU only.
2262
2263        simeth=         [IA-64]
2264        simscsi=
2265
2266        slram=          [HW,MTD]
2267
2268        slub_debug[=options[,slabs]]    [MM, SLUB]
2269                        Enabling slub_debug allows one to determine the
2270                        culprit if slab objects become corrupted. Enabling
2271                        slub_debug can create guard zones around objects and
2272                        may poison objects when not in use. Also tracks the
2273                        last alloc / free. For more information see
2274                        Documentation/vm/slub.txt.
2275
2276        slub_max_order= [MM, SLUB]
2277                        Determines the maximum allowed order for slabs.
2278                        A high setting may cause OOMs due to memory
2279                        fragmentation. For more information see
2280                        Documentation/vm/slub.txt.
2281
2282        slub_min_objects=       [MM, SLUB]
2283                        The minimum number of objects per slab. SLUB will
2284                        increase the slab order up to slub_max_order to
2285                        generate a sufficiently large slab able to contain
2286                        the number of objects indicated. The higher the number
2287                        of objects the smaller the overhead of tracking slabs
2288                        and the less frequently locks need to be acquired.
2289                        For more information see Documentation/vm/slub.txt.
2290
2291        slub_min_order= [MM, SLUB]
2292                        Determines the mininum page order for slabs. Must be
2293                        lower than slub_max_order.
2294                        For more information see Documentation/vm/slub.txt.
2295
2296        slub_nomerge    [MM, SLUB]
2297                        Disable merging of slabs with similar size. May be
2298                        necessary if there is some reason to distinguish
2299                        allocs to different slabs. Debug options disable
2300                        merging on their own.
2301                        For more information see Documentation/vm/slub.txt.
2302
2303        smart2=         [HW]
2304                        Format: <io1>[,<io2>[,...,<io8>]]
2305
2306        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2307                        attempt to substitute SMP alternatives once at boot.
2308
2309        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2310        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2311        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2312        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2313        smsc-ircc2.ircc_irq=    [HW] IRQ line
2314        smsc-ircc2.ircc_dma=    [HW] DMA channel
2315        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2316                                0: Toshiba Satellite 1800 (GP data pin select)
2317                                1: Fast pin select (default)
2318                                2: ATC IRMode
2319
2320        softlockup_panic=
2321                        [KNL] Should the soft-lockup detector generate panics.
2322
2323        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2324                        See Documentation/sonypi.txt
2325
2326        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2327                        See Documentation/serial/specialix.txt.
2328
2329        spia_io_base=   [HW,MTD]
2330        spia_fio_base=
2331        spia_pedr=
2332        spia_peddr=
2333
2334        stacktrace      [FTRACE]
2335                        Enabled the stack tracer on boot up.
2336
2337        sti=            [PARISC,HW]
2338                        Format: <num>
2339                        Set the STI (builtin display/keyboard on the HP-PARISC
2340                        machines) console (graphic card) which should be used
2341                        as the initial boot-console.
2342                        See also comment in drivers/video/console/sticore.c.
2343
2344        sti_font=       [HW]
2345                        See comment in drivers/video/console/sticore.c.
2346
2347        stifb=          [HW]
2348                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2349
2350        sunrpc.min_resvport=
2351        sunrpc.max_resvport=
2352                        [NFS,SUNRPC]
2353                        SunRPC servers often require that client requests
2354                        originate from a privileged port (i.e. a port in the
2355                        range 0 < portnr < 1024).
2356                        An administrator who wishes to reserve some of these
2357                        ports for other uses may adjust the range that the
2358                        kernel's sunrpc client considers to be privileged
2359                        using these two parameters to set the minimum and
2360                        maximum port values.
2361
2362        sunrpc.pool_mode=
2363                        [NFS]
2364                        Control how the NFS server code allocates CPUs to
2365                        service thread pools.  Depending on how many NICs
2366                        you have and where their interrupts are bound, this
2367                        option will affect which CPUs will do NFS serving.
2368                        Note: this parameter cannot be changed while the
2369                        NFS server is running.
2370
2371                        auto        the server chooses an appropriate mode
2372                                    automatically using heuristics
2373                        global      a single global pool contains all CPUs
2374                        percpu      one pool for each CPU
2375                        pernode     one pool for each NUMA node (equivalent
2376                                    to global on non-NUMA machines)
2377
2378        sunrpc.tcp_slot_table_entries=
2379        sunrpc.udp_slot_table_entries=
2380                        [NFS,SUNRPC]
2381                        Sets the upper limit on the number of simultaneous
2382                        RPC calls that can be sent from the client to a
2383                        server. Increasing these values may allow you to
2384                        improve throughput, but will also increase the
2385                        amount of memory reserved for use by the client.
2386
2387        swapaccount[=0|1]
2388                        [KNL] Enable accounting of swap in memory resource
2389                        controller if no parameter or 1 is given or disable
2390                        it if 0 is given (See Documentation/cgroups/memory.txt)
2391
2392        swiotlb=        [IA-64] Number of I/O TLB slabs
2393
2394        switches=       [HW,M68k]
2395
2396        sysfs.deprecated=0|1 [KNL]
2397                        Enable/disable old style sysfs layout for old udev
2398                        on older distributions. When this option is enabled
2399                        very new udev will not work anymore. When this option
2400                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2401                        in older udev will not work anymore.
2402                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2403                        the kernel configuration.
2404
2405        sysrq_always_enabled
2406                        [KNL]
2407                        Ignore sysrq setting - this boot parameter will
2408                        neutralize any effect of /proc/sys/kernel/sysrq.
2409                        Useful for debugging.
2410
2411        tdfx=           [HW,DRM]
2412
2413        test_suspend=   [SUSPEND]
2414                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2415                        standby suspend) as the system sleep state to briefly
2416                        enter during system startup.  The system is woken from
2417                        this state using a wakeup-capable RTC alarm.
2418
2419        thash_entries=  [KNL,NET]
2420                        Set number of hash buckets for TCP connection
2421
2422        thermal.act=    [HW,ACPI]
2423                        -1: disable all active trip points in all thermal zones
2424                        <degrees C>: override all lowest active trip points
2425
2426        thermal.crt=    [HW,ACPI]
2427                        -1: disable all critical trip points in all thermal zones
2428                        <degrees C>: override all critical trip points
2429
2430        thermal.nocrt=  [HW,ACPI]
2431                        Set to disable actions on ACPI thermal zone
2432                        critical and hot trip points.
2433
2434        thermal.off=    [HW,ACPI]
2435                        1: disable ACPI thermal control
2436
2437        thermal.psv=    [HW,ACPI]
2438                        -1: disable all passive trip points
2439                        <degrees C>: override all passive trip points to this
2440                        value
2441
2442        thermal.tzp=    [HW,ACPI]
2443                        Specify global default ACPI thermal zone polling rate
2444                        <deci-seconds>: poll all this frequency
2445                        0: no polling (default)
2446
2447        topology=       [S390]
2448                        Format: {off | on}
2449                        Specify if the kernel should make use of the cpu
2450                        topology informations if the hardware supports these.
2451                        The scheduler will make use of these informations and
2452                        e.g. base its process migration decisions on it.
2453                        Default is on.
2454
2455        tp720=          [HW,PS2]
2456
2457        tpm_suspend_pcr=[HW,TPM]
2458                        Format: integer pcr id
2459                        Specify that at suspend time, the tpm driver
2460                        should extend the specified pcr with zeros,
2461                        as a workaround for some chips which fail to
2462                        flush the last written pcr on TPM_SaveState.
2463                        This will guarantee that all the other pcrs
2464                        are saved.
2465
2466        trace_buf_size=nn[KMG]
2467                        [FTRACE] will set tracing buffer size.
2468
2469        trace_event=[event-list]
2470                        [FTRACE] Set and start specified trace events in order
2471                        to facilitate early boot debugging.
2472                        See also Documentation/trace/events.txt
2473
2474        tsc=            Disable clocksource stability checks for TSC.
2475                        Format: <string>
2476                        [x86] reliable: mark tsc clocksource as reliable, this
2477                        disables clocksource verification at runtime, as well
2478                        as the stability checks done at bootup. Used to enable
2479                        high-resolution timer mode on older hardware, and in
2480                        virtualized environment.
2481                        [x86] noirqtime: Do not use TSC to do irq accounting.
2482                        Used to run time disable IRQ_TIME_ACCOUNTING on any
2483                        platforms where RDTSC is slow and this accounting
2484                        can add overhead.
2485
2486        turbografx.map[2|3]=    [HW,JOY]
2487                        TurboGraFX parallel port interface
2488                        Format:
2489                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2490                        See also Documentation/input/joystick-parport.txt
2491
2492        uhash_entries=  [KNL,NET]
2493                        Set number of hash buckets for UDP/UDP-Lite connections
2494
2495        uhci-hcd.ignore_oc=
2496                        [USB] Ignore overcurrent events (default N).
2497                        Some badly-designed motherboards generate lots of
2498                        bogus events, for ports that aren't wired to
2499                        anything.  Set this parameter to avoid log spamming.
2500                        Note that genuine overcurrent events won't be
2501                        reported either.
2502
2503        unknown_nmi_panic
2504                        [X86]
2505                        Set unknown_nmi_panic=1 early on boot.
2506
2507        usbcore.autosuspend=
2508                        [USB] The autosuspend time delay (in seconds) used
2509                        for newly-detected USB devices (default 2).  This
2510                        is the time required before an idle device will be
2511                        autosuspended.  Devices for which the delay is set
2512                        to a negative value won't be autosuspended at all.
2513
2514        usbcore.usbfs_snoop=
2515                        [USB] Set to log all usbfs traffic (default 0 = off).
2516
2517        usbcore.blinkenlights=
2518                        [USB] Set to cycle leds on hubs (default 0 = off).
2519
2520        usbcore.old_scheme_first=
2521                        [USB] Start with the old device initialization
2522                        scheme (default 0 = off).
2523
2524        usbcore.use_both_schemes=
2525                        [USB] Try the other device initialization scheme
2526                        if the first one fails (default 1 = enabled).
2527
2528        usbcore.initial_descriptor_timeout=
2529                        [USB] Specifies timeout for the initial 64-byte
2530                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2531                        (default 5000 = 5.0 seconds).
2532
2533        usbhid.mousepoll=
2534                        [USBHID] The interval which mice are to be polled at.
2535
2536        usb-storage.delay_use=
2537                        [UMS] The delay in seconds before a new device is
2538                        scanned for Logical Units (default 5).
2539
2540        usb-storage.quirks=
2541                        [UMS] A list of quirks entries to supplement or
2542                        override the built-in unusual_devs list.  List
2543                        entries are separated by commas.  Each entry has
2544                        the form VID:PID:Flags where VID and PID are Vendor
2545                        and Product ID values (4-digit hex numbers) and
2546                        Flags is a set of characters, each corresponding
2547                        to a common usb-storage quirk flag as follows:
2548                                a = SANE_SENSE (collect more than 18 bytes
2549                                        of sense data);
2550                                b = BAD_SENSE (don't collect more than 18
2551                                        bytes of sense data);
2552                                c = FIX_CAPACITY (decrease the reported
2553                                        device capacity by one sector);
2554                                h = CAPACITY_HEURISTICS (decrease the
2555                                        reported device capacity by one
2556                                        sector if the number is odd);
2557                                i = IGNORE_DEVICE (don't bind to this
2558                                        device);
2559                                l = NOT_LOCKABLE (don't try to lock and
2560                                        unlock ejectable media);
2561                                m = MAX_SECTORS_64 (don't transfer more
2562                                        than 64 sectors = 32 KB at a time);
2563                                o = CAPACITY_OK (accept the capacity
2564                                        reported by the device);
2565                                r = IGNORE_RESIDUE (the device reports
2566                                        bogus residue values);
2567                                s = SINGLE_LUN (the device has only one
2568                                        Logical Unit);
2569                                w = NO_WP_DETECT (don't test whether the
2570                                        medium is write-protected).
2571                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2572
2573        userpte=
2574                        [X86] Flags controlling user PTE allocations.
2575
2576                                nohigh = do not allocate PTE pages in
2577                                        HIGHMEM regardless of setting
2578                                        of CONFIG_HIGHPTE.
2579
2580        vdso=           [X86,SH]
2581                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2582                        vdso=1: enable VDSO (default)
2583                        vdso=0: disable VDSO mapping
2584
2585        vdso32=         [X86]
2586                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2587                        vdso32=1: enable 32-bit VDSO (default)
2588                        vdso32=0: disable 32-bit VDSO mapping
2589
2590        vector=         [IA-64,SMP]
2591                        vector=percpu: enable percpu vector domain
2592
2593        video=          [FB] Frame buffer configuration
2594                        See Documentation/fb/modedb.txt.
2595
2596        vga=            [BOOT,X86-32] Select a particular video mode
2597                        See Documentation/x86/boot.txt and
2598                        Documentation/svga.txt.
2599                        Use vga=ask for menu.
2600                        This is actually a boot loader parameter; the value is
2601                        passed to the kernel using a special protocol.
2602
2603        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2604                        size of <nn>. This can be used to increase the
2605                        minimum size (128MB on x86). It can also be used to
2606                        decrease the size and leave more room for directly
2607                        mapped kernel RAM.
2608
2609        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
2610                        Format: <command>
2611
2612        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
2613                        Format: <command>
2614
2615        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
2616                        Format: <command>
2617
2618        vt.cur_default= [VT] Default cursor shape.
2619                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
2620                        the parameters of the <Esc>[?A;B;Cc escape sequence;
2621                        see VGA-softcursor.txt. Default: 2 = underline.
2622
2623        vt.default_blu= [VT]
2624                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2625                        Change the default blue palette of the console.
2626                        This is a 16-member array composed of values
2627                        ranging from 0-255.
2628
2629        vt.default_grn= [VT]
2630                        Format: <green0>,<green1>,<green2>,...,<green15>
2631                        Change the default green palette of the console.
2632                        This is a 16-member array composed of values
2633                        ranging from 0-255.
2634
2635        vt.default_red= [VT]
2636                        Format: <red0>,<red1>,<red2>,...,<red15>
2637                        Change the default red palette of the console.
2638                        This is a 16-member array composed of values
2639                        ranging from 0-255.
2640
2641        vt.default_utf8=
2642                        [VT]
2643                        Format=<0|1>
2644                        Set system-wide default UTF-8 mode for all tty's.
2645                        Default is 1, i.e. UTF-8 mode is enabled for all
2646                        newly opened terminals.
2647
2648        vt.global_cursor_default=
2649                        [VT]
2650                        Format=<-1|0|1>
2651                        Set system-wide default for whether a cursor
2652                        is shown on new VTs. Default is -1,
2653                        i.e. cursors will be created by default unless
2654                        overridden by individual drivers. 0 will hide
2655                        cursors, 1 will display them.
2656
2657        watchdog timers [HW,WDT] For information on watchdog timers,
2658                        see Documentation/watchdog/watchdog-parameters.txt
2659                        or other driver-specific files in the
2660                        Documentation/watchdog/ directory.
2661
2662        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
2663                        default x2apic cluster mode on platforms
2664                        supporting x2apic.
2665
2666        x86_mrst_timer= [X86-32,APBT]
2667                        Choose timer option for x86 Moorestown MID platform.
2668                        Two valid options are apbt timer only and lapic timer
2669                        plus one apbt timer for broadcast timer.
2670                        x86_mrst_timer=apbt_only | lapic_and_apbt
2671
2672        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2673        xd_geo=         See header of drivers/block/xd.c.
2674
2675        xen_emul_unplug=                [HW,X86,XEN]
2676                        Unplug Xen emulated devices
2677                        Format: [unplug0,][unplug1]
2678                        ide-disks -- unplug primary master IDE devices
2679                        aux-ide-disks -- unplug non-primary-master IDE devices
2680                        nics -- unplug network devices
2681                        all -- unplug all emulated devices (NICs and IDE disks)
2682                        unnecessary -- unplugging emulated devices is
2683                                unnecessary even if the host did not respond to
2684                                the unplug protocol
2685                        never -- do not unplug even if version check succeeds
2686
2687        xirc2ps_cs=     [NET,PCMCIA]
2688                        Format:
2689                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2690
2691______________________________________________________________________
2692
2693TODO:
2694
2695        Add more DRM drivers.
2696
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